Evaluating syntactic comprehension during awake intraoperative cortical stimulation mapping

OBJECTIVE Electrocortical stimulation mapping (ECS) is widely used to identify essential language areas, but sentence-level processing has rarely been investigated. METHODS While undergoing awake surgery in the dominant left hemisphere, 6 subjects were asked to comprehend sentences varying in their demands on syntactic processing. RESULTS In all 6 subjects, stimulation of the inferior frontal gyrus disrupted comprehension of passive sentences, which critically depend on syntactic processing to correctly assign grammatical roles, without disrupting comprehension of simpler tasks. In 4 of the 6 subjects, these sites were localized to the pars opercularis. Sentence comprehension was also disrupted by stimulation of other perisylvian sites, but in a more variable manner. CONCLUSIONS These findings suggest that there may be language regions that differentially contribute to sentence processing and which therefore are best identified using sentence-level tasks. The functional consequences of resecting these sites remain to be investigated.

Automated summary

Electrocortical stimulation mapping (ECS) was used during awake surgery in 6 patients to investigate sentence-level processing. Stimulation of the inferior frontal gyrus disrupted comprehension of passive sentences in all subjects, while simpler tasks remained unaffected. These findings suggest the presence of language regions that contribute differently to sentence processing, and sentence-level tasks are best for identifying them. The functional consequences of resecting these sites need further investigation.